It can sometimes be a bad idea to mix your hobbies and try to make an income out of them, because it can eventually suck out all the energy or the original reason that attracted you to it in the first place.
It depends. It could make someone feel burnt out if the hobby that they used to do as a de-stressing activity is now the thing that is making them stressed. But I would argue that stressing over something you like is a lot more preferable than stressing over something you don’t like. If I am being stressed over my hobby/job probably because I care about it a lot. So you can’t complain too much. I’d rather have that than do something I totally despise.